The embodiment relates to an apparatus for measuring convergence and ceiling subsidence using a fiber bragg grating sensor, and more particularly, to an apparatus for measuring convergence and ceiling subsidence using a fiber bragg grating sensor, which measures convergence and ceiling subsidence in real time while constructing and maintaining a tunnel.
In case of measuring the convergence of a tunnel, when a variation on a section of the tunnel only in a longitudinal direction is measured, since the directionality of coordinates cannot be known due to the strain property of lining after the lining is strained, if it is not known whether a tunnel is contracted or expanded, it is difficult to precisely measure the convergence of the tunnel.
Thus, according to a method of measuring convergence and ceiling subsidence, a length variation measuring sensor is buried while passing through the lining of a tunnel such that it is determined whether a tunnel is contracted or expanded. Differently, after degrees of length and angle variations are measured by using displacement and angle sensors for measuring convergence, two measurement results are combined with each other to be converted into convergence.
Since an electric sensor system utilizing the latter measures two kinds of values in connection with length and angle variations in mutually different measuring schemes, the accuracy of convergence measurement is dependent on the mutually different measurement accuracies of two kinds of sensors. In addition, since two-kinds of sensor systems are used, a device of collecting data is complex and the measuring cost is relatively increased.
Further, when a measurement length is 1 m, since a sensor having resolution of 1/100 mm and 1/100 degree is mainly used, there is a limit to measure a micro-strain.
In addition, as the measurement reliability is deteriorated due to effects of electromagnetic waves, the measurement cannot be performed while the subway is operated.
To solve the problems, the applicant has filed techniques of measuring convergence and ceiling subsidence by using a plurality of fiber bragg grating sensors as disclosed in following patent documents 1 and 2, which have been registered now.
However, an apparatus for measuring convergence and ceiling subsidence according to the related art including the patent document 1 and 2 includes a fiber bragg grating sensor mounted on a flat surface, so that there is a limit in the accuracy of 2D and 3D measurements.
However, when a gap is generated due to an interference substance formed on a target object on which an apparatus for measuring convergence and ceiling subsidence according to the related art will be mounted, it is difficult to mount the apparatus for measuring convergence and ceiling subsidence, so that the accuracy of a measured value is greatly deteriorated.
In addition, an apparatus for measuring convergence and ceiling subsidence according to the related art includes an angle displacement sensor mounted on a strain sensor, so that an error occurs in the measured value of length displacement due to a weight of the angle displacement sensor.